Method of converting materials containing lead sulphide to oxygenated compounds



. Nov. 17, 1931. A. HOLMES ET-AL ING LEA NDS METHOD OF CONVERTINGMATERIALS CONTAIN SULPHIDE TO OXYGENATED COMPOU Filed June 22, 1927 viCm mw QOU Patented Nov. 17, 1931 UNiTED stares AUGUST HOLMES, 0F NEWARK,AND LOUIS BUBGESS, OF ROSELLE, NEW JERSEY, AS-

SIGNORS TO STANDARD OIL DEVELOPMENT COMPANY, A CORPORATTON OF WARE DELA-METHOD or CONVERTING MATERIALS CONTAINING LEAD sULPHIDn To OXYGENATEDCOMPOUNDS Application mea June 22,

This invention relates to the conversion of lead sulphide, or materialscontaining the same, to oxygenated compounds of lead and has for itsobjects, the more efficient and economical conversion thereof.

Lead sulphides and residues containing same are produced in certainoperations. A solution Iof litharge in caustic is used in the petroleumindustry for the treatment of distillates and a residue containing leadsulphide settles out or may be separated from this solution or from theoil after such treatment. A particularly advantageous use of our processis in the reconversion of such residues to a form in Which they may beagain used in the treatment `of petroleum distillates. In accordanceWith our process lead sulphide or residues containing same are mixedwith alkali metal carbonate or bicarbonate and roasted in contact withan oxidizing gas. The term oxidizing gas comprehends either a gascontaining elemental oxygen or conr pounds which will yield oxygen tothe sulphide-bearing materials. The proportionof carbonate orbicarbonate used may vary over considerable limits b ut is preferably soad justed as to furnish an equivalent of Nag() for each equivalent ofS03 in the finished product. Under these conditions the reaction productconsists of lead oxide and sodium sulphate. However, the product may bemade to contain double compounds of sodium and lead by increasing' theamount of carbonate or bicarbonate added. In practice, We find itpreferable to add lO-20% by Weight of sodium carbonate based on the leadsulphide present in the material charged. The roasting is preferablycarried out at temperatures below that at Which the charge melts orbecomes pasty and temperatures between 500800 C. are preferred. The timeof heating should be such as to insure substantially complete oxidationof the lead sulphide in the original charge and may vary from a 'fewminutes to several hours, depending on the temperature, porosity andcomposition of the charge. The heating may be indirect, an atmosphereyielding oxygen being supplied in any suitable manner or may be direct,in which case oxidation Will result trom the the desired temperature.

1927. Serial No.7200,537.

gases `necessarily present and these should,

heated by a burner located at ythe discharge y end. rlfliesulphide-bearing material and car-V bonatev or bicarbonate may lbeVpremlxed or added separately 1n which event mixing Will `take place inthe cooler end ot' the cylinder.

The burner preferably operated so that the material discharged will havea' Uemperature of 50G-800 C. The roasted material is cooled in anysuitable manner. t may be dissolved `in causticV solution andtherebymade available for reuse in treating petroleum distillates.Solution in caustic is accelerated by mixing and heating.

The accompanying dra-Wing shows a longitudinal section of apparatussuitable for carrying out the process. Our preferred method of operationWill be described With reference thereto. The hopper l contains a supplyof sulphide-bearing residue mixed with the desired quantity of carbonateo1' bicarbonate. This is fed continuously by means for Worm conveyor 2,actuated in any suitable manner to the kiln 3. Gaseous products ofcombustion escape by means of stack 4. The `kiln 3 is lined withrefractory material 3a and is carried by rings 5 bearing` on Wheels 6.It is causedto rotate by any suitableV mechanism such as a motor.operating speed reducer 7, which in turn actuates the driving gear 8and the ring gear 9. Because ot' this rotation, materials charged movegradually toward the lower end of the cylin der and are heated by meansof burner 18 to The heated materials discharged vthrough chute 19 intocooler l0, which is a steel shell rotated in the saine manner as thelrilnl and preferably equipped With a series ot' longitudinal vanes 11,Which alternately lift and then drop the material. l The cooled materialis discharged from the lower end of the kiln into tank l2 which maybesupplied by a solution of caustic in any manner, of. by means of pipe13. The contents of the tank may be heated and mixed by means of steamfrom the valved pipe 14 introduced into the tank through distributor 515. Then desired, the solution may be Withdrawn through Valved pipe 16by means of pump 17. y

It Will be understood that the apparatus shown is in illustration merelyand that the l process is not in any Way limited thereby.

We claim:

1. The method of converting lead compounds, contained in residuesobtained from treatment oi petroleum distillates Withran aqueoussolution of lead oXide in caustic alkali, to an oxide of lead, whichcomprises adding an alkali metal carbonate to the residues and heating"the same in contact With a tQ'as capable of yielding oxygen thereto.

20 2. The method oi converting lead compounds, contained in residuesobtained from treatment of petroleum distillates with an aoueonssolution of lead oxide in caustic alkali. to an. oxide of lead, whichcomprises adding' an alkali metal carbonate to the residues. heating thesame in Contact With a gas capable of yielding oxygen tothe material,and dissolving` the oxide'of lead produced in an aqueous solution of acaustic alkali for use in further treatment of petroleum distillates.

3. Method according` to claim 1, in which the heating,r is carried outat temperatures between 500O and 800 C.

5 4L. Method according to claim 1, in which the mixture or" residues andalkali metal carbonate passes in counter current relation to Y the hotgases.

AUGUST HOLMES. :0 LOUIS BURGESS.

